[PATCH -v5 3/4] cifs NTLMv2/NTLMSSP define crypto hash functions and create and send keys needed for key exchange

[shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org]

From: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>


Mark dependency on crypto modules in Kconfig.

Defining per structures sdesc and cifs_secmech which are used to store
crypto hash functions and contexts.  They are stored per smb connection
and used for all auth mechs to genereate hash values and signatures.

Allocate crypto hashing functions, security descriptiors, and respective
contexts when a smb/tcp connection is established.
Release them when a tcp/smb connection is taken down.

md5 and hmac-md5 are two crypto hashing functions that are used
throught the life of an smb/tcp connection by various functions that
calcualte signagure and ntlmv2 hash, HMAC etc.

structure ntlmssp_auth and filed cphready is defined as per smb connection.

ntlmssp_auth holds secondary key which is a nonce that gets used as a key
to generate signatures, ciphertext is genereated by rc4/arc4 encryption of
secondary key using ntlmv2 session key and sent in the session key field of
the type 3 message sent by the client during ntlmssp negotiation/exchange
These are per session structures and secondary key and cipher text
get calculated only once per smb connection, during first smb session setup
for that smb connection.

Field cphready is used to mark such that once secondary keys and ciphertext
are calculated during very first smb session setup for a smb connection
and ciphertext is sent to the server, the same does not happen during
subsequent smb session setups/establishments.

A key is exchanged with the server if client indicates so in flags in
type 1 messsage and server agrees in flag in type 2 message of ntlmssp
negotiation.  If both client and agree, a key sent by client in
type 3 message of ntlmssp negotiation in the session key field.
The key is a ciphertext generated off of secondary key, a nonce, using
ntlmv2 hash via rc4/arc4.

If authentication is successful, the secondary key is the that client
uses to calculate cifs/smb signature in the messages that client sends
and to verify the messages sent by server.
This key stays with the smb connection for its life and is the key used
to generate (and verify) signatures for all the subsequent smb sessions
for this smb connection.

So only for the first smb session on any smb connection, type 1 message
of ntlmssp negotiation selects the flag NTLMSSP_NEGOTIATE_KEY_XCH.
It is not used for subsequent smb sessions on this smb connection i.e.
no need to generate secondary key, create ciphertext and send it etc.

After the very first successful smb session, sequence number gets set
to 0 and  variable cphready is used to mark that the key calculations
are done. cphready is reset when a reconnect of the smb connection
happens as sessions get set up again.

Calculation of ciphertext and setting cphready, is done within
mutex lock to prevent race of smb session setups on a new smb connection.


Signed-off-by: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 fs/cifs/Kconfig       |    3 +
 fs/cifs/cifsencrypt.c |  125 +++++++++++++++++++++++++++++++++++++++++++++++++
 fs/cifs/cifsglob.h    |   28 +++++++++++
 fs/cifs/cifspdu.h     |    7 +++
 fs/cifs/cifsproto.h   |    3 +
 fs/cifs/connect.c     |   18 ++++++-
 fs/cifs/sess.c        |   26 +++++++---
 7 files changed, 200 insertions(+), 10 deletions(-)

diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index 917b7d4..0ed2139 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -2,6 +2,9 @@ config CIFS
 	tristate "CIFS support (advanced network filesystem, SMBFS successor)"
 	depends on INET
 	select NLS
+	select CRYPTO
+	select CRYPTO_MD5
+	select CRYPTO_ARC4
 	help
 	  This is the client VFS module for the Common Internet File System
 	  (CIFS) protocol which is the successor to the Server Message Block
diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index ab0533a..bd97543 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -481,3 +481,128 @@ void CalcNTLMv2_response(const struct cifsSesInfo *ses,
 	hmac_md5_final(v2_session_response, &context);
 /*	cifs_dump_mem("v2_sess_rsp: ", v2_session_response, 32); */
 }
+
+int
+calc_seckey(struct TCP_Server_Info *server)
+{
+	int rc;
+	struct crypto_blkcipher *tfm_arc4;
+	struct scatterlist sgin, sgout;
+	struct blkcipher_desc desc;
+
+	if (!server) {
+		cERROR(1, "%s: Can't determine ciphertext key\n", __func__);
+		return 1;
+	}
+
+	mutex_lock(&server->srv_mutex);
+	if (server->cphready) {
+		mutex_unlock(&server->srv_mutex);
+		return 0;
+	}
+
+	get_random_bytes(server->ntlmssp.sec_key, CIFS_NTLMV2_SESSKEY_SIZE);
+
+	tfm_arc4 = crypto_alloc_blkcipher("ecb(arc4)",
+						0, CRYPTO_ALG_ASYNC);
+	if (!tfm_arc4 || IS_ERR(tfm_arc4)) {
+		cERROR(1, "could not allocate crypto API arc4\n");
+		mutex_unlock(&server->srv_mutex);
+		return PTR_ERR(tfm_arc4);
+	}
+
+	desc.tfm = tfm_arc4;
+
+	crypto_blkcipher_setkey(tfm_arc4, server->session_key.data.ntlmv2.key,
+					CIFS_CPHTXT_SIZE);
+
+	sg_init_one(&sgin, server->ntlmssp.sec_key, CIFS_CPHTXT_SIZE);
+	sg_init_one(&sgout, server->ntlmssp.ciphertext, CIFS_CPHTXT_SIZE);
+
+	rc = crypto_blkcipher_encrypt(&desc, &sgout, &sgin, CIFS_CPHTXT_SIZE);
+	if (rc) {
+		cERROR(1, "could not encrypt session key rc: %d\n", rc);
+		crypto_free_blkcipher(tfm_arc4);
+		mutex_unlock(&server->srv_mutex);
+		return rc;
+	}
+
+	crypto_free_blkcipher(tfm_arc4);
+
+	server->sequence_number = 0;
+	server->cphready = true;
+	mutex_unlock(&server->srv_mutex);
+
+	return 0;
+}
+
+void
+cifs_crypto_shash_release(struct TCP_Server_Info *server)
+{
+	if (server->secmech.md5)
+		crypto_free_shash(server->secmech.md5);
+
+	if (server->secmech.hmacmd5)
+		crypto_free_shash(server->secmech.hmacmd5);
+
+	kfree(server->secmech.sdeschmacmd5);
+
+	kfree(server->secmech.sdescmd5);
+}
+
+int
+cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
+{
+	int rc;
+	unsigned int size;
+
+	server->secmech.hmacmd5 = crypto_alloc_shash("hmac(md5)", 0, 0);
+	if (!server->secmech.hmacmd5 ||
+			IS_ERR(server->secmech.hmacmd5)) {
+		cERROR(1, "could not allocate crypto hmacmd5\n");
+		return PTR_ERR(server->secmech.hmacmd5);
+	}
+
+	server->secmech.md5 = crypto_alloc_shash("md5", 0, 0);
+	if (!server->secmech.md5 || IS_ERR(server->secmech.md5)) {
+		cERROR(1, "could not allocate crypto md5\n");
+		rc = PTR_ERR(server->secmech.md5);
+		goto crypto_allocate_md5_fail;
+	}
+
+	size = sizeof(struct shash_desc) +
+			crypto_shash_descsize(server->secmech.hmacmd5);
+	server->secmech.sdeschmacmd5 = kmalloc(size, GFP_KERNEL);
+	if (!server->secmech.sdeschmacmd5) {
+		cERROR(1, "cifs_crypto_shash_allocate: can't alloc hmacmd5\n");
+		rc = -ENOMEM;
+		goto crypto_allocate_hmacmd5_sdesc_fail;
+	}
+	server->secmech.sdeschmacmd5->shash.tfm = server->secmech.hmacmd5;
+	server->secmech.sdeschmacmd5->shash.flags = 0x0;
+
+
+	size = sizeof(struct shash_desc) +
+			crypto_shash_descsize(server->secmech.md5);
+	server->secmech.sdescmd5 = kmalloc(size, GFP_KERNEL);
+	if (!server->secmech.sdescmd5) {
+		cERROR(1, "cifs_crypto_shash_allocate: can't alloc md5\n");
+		rc = -ENOMEM;
+		goto crypto_allocate_md5_sdesc_fail;
+	}
+	server->secmech.sdescmd5->shash.tfm = server->secmech.md5;
+	server->secmech.sdescmd5->shash.flags = 0x0;
+
+	return 0;
+
+crypto_allocate_md5_sdesc_fail:
+	kfree(server->secmech.sdeschmacmd5);
+
+crypto_allocate_hmacmd5_sdesc_fail:
+	crypto_free_shash(server->secmech.md5);
+
+crypto_allocate_md5_fail:
+	crypto_free_shash(server->secmech.hmacmd5);
+
+	return rc;
+}
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index c68f31c..c7da866 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -25,6 +25,9 @@
 #include <linux/workqueue.h>
 #include "cifs_fs_sb.h"
 #include "cifsacl.h"
+#include <crypto/internal/hash.h>
+#include <linux/scatterlist.h>
+
 /*
  * The sizes of various internal tables and strings
  */
@@ -109,6 +112,28 @@ struct session_key {
 	} data;
 };
 
+/* crypto security descriptor definition */
+struct sdesc {
+	struct shash_desc shash;
+	char ctx[];
+};
+
+/* crypto hashing related structure/fields, not speicific to a sec mech */
+struct cifs_secmech {
+	struct crypto_shash *hmacmd5; /* hmac-md5 hash function */
+	struct crypto_shash *md5; /* md5 hash function */
+	struct sdesc *sdeschmacmd5;  /* ctxt to generate ntlmv2 hash, CR1 */
+	struct sdesc *sdescmd5; /* ctxt to generate cifs/smb signature */
+};
+
+/* per smb connection structure/fields */
+struct ntlmssp_auth {
+	__u32 client_flags; /* sent by client in type 1 ntlmsssp exchange */
+	__u32 server_flags; /* sent by server in type 2 ntlmssp exchange */
+	unsigned char sec_key[CIFS_CPHTXT_SIZE]; /* a nonce client generates */
+	unsigned char ciphertext[CIFS_CPHTXT_SIZE]; /* sent to server */
+};
+
 struct cifs_cred {
 	int uid;
 	int gid;
@@ -187,6 +212,9 @@ struct TCP_Server_Info {
 	unsigned long lstrp; /* when we got last response from this server */
 	u16 dialect; /* dialect index that server chose */
 	/* extended security flavors that server supports */
+	struct cifs_secmech secmech; /* crypto sec mech functs, descriptors */
+	struct ntlmssp_auth ntlmssp; /* sec key, ciphertext, flags */
+	bool    cphready;               /* ciphertext is calculated */
 	bool	sec_kerberos;		/* supports plain Kerberos */
 	bool	sec_mskerberos;		/* supports legacy MS Kerberos */
 	bool	sec_kerberosu2u;	/* supports U2U Kerberos */
diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
index b0f4b56..dc90a36 100644
--- a/fs/cifs/cifspdu.h
+++ b/fs/cifs/cifspdu.h
@@ -134,6 +134,13 @@
  * Size of the session key (crypto key encrypted with the password
  */
 #define CIFS_SESS_KEY_SIZE (24)
+#define CIFS_CLIENT_CHALLENGE_SIZE (8)
+#define CIFS_SERVER_CHALLENGE_SIZE (8)
+#define CIFS_HMAC_MD5_HASH_SIZE (16)
+#define CIFS_CPHTXT_SIZE (16)
+#define CIFS_NTLMV2_SESSKEY_SIZE (16)
+#define CIFS_NTHASH_SIZE (16)
+
 
 /*
  * Maximum user name length
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index c155479..d89a87a 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -369,6 +369,9 @@ extern int cifs_calculate_session_key(struct session_key *key, const char *rn,
 extern void CalcNTLMv2_response(const struct cifsSesInfo *, char *);
 extern int setup_ntlmv2_rsp(struct cifsSesInfo *, char *,
 			     const struct nls_table *);
+extern int cifs_crypto_shash_allocate(struct TCP_Server_Info *);
+extern void cifs_crypto_shash_release(struct TCP_Server_Info *);
+extern int calc_seckey(struct TCP_Server_Info *);
 #ifdef CONFIG_CIFS_WEAK_PW_HASH
 extern void calc_lanman_hash(const char *password, const char *cryptkey,
 				bool encrypt, char *lnm_session_key);
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index c99760a..4818089 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -199,6 +199,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 			if (server->tcpStatus != CifsExiting)
 				server->tcpStatus = CifsGood;
 			server->sequence_number = 0;
+			server->cphready = false;
 			spin_unlock(&GlobalMid_Lock);
 	/*		atomic_set(&server->inFlight,0);*/
 			wake_up(&server->response_q);
@@ -1502,6 +1503,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server)
 	server->tcpStatus = CifsExiting;
 	spin_unlock(&GlobalMid_Lock);
 
+	cifs_crypto_shash_release(server);
 	cifs_fscache_release_client_cookie(server);
 
 	task = xchg(&server->tsk, NULL);
@@ -1556,12 +1558,19 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 		goto out_err;
 	}
 
+	rc = cifs_crypto_shash_allocate(tcp_ses);
+	if (rc) {
+		cERROR(1, "could not setup hash structures rc %d", rc);
+		goto out_err;
+	}
+
 	tcp_ses->hostname = extract_hostname(volume_info->UNC);
 	if (IS_ERR(tcp_ses->hostname)) {
 		rc = PTR_ERR(tcp_ses->hostname);
-		goto out_err;
+		goto out_err2;
 	}
 
+	tcp_ses->cphready = false;
 	tcp_ses->noblocksnd = volume_info->noblocksnd;
 	tcp_ses->noautotune = volume_info->noautotune;
 	tcp_ses->tcp_nodelay = volume_info->sockopt_tcp_nodelay;
@@ -1600,7 +1609,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 	}
 	if (rc < 0) {
 		cERROR(1, "Error connecting to socket. Aborting operation");
-		goto out_err;
+		goto out_err2;
 	}
 
 	/*
@@ -1614,7 +1623,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 		rc = PTR_ERR(tcp_ses->tsk);
 		cERROR(1, "error %d create cifsd thread", rc);
 		module_put(THIS_MODULE);
-		goto out_err;
+		goto out_err2;
 	}
 
 	/* thread spawned, put it on the list */
@@ -1626,6 +1635,9 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 
 	return tcp_ses;
 
+out_err2:
+	cifs_crypto_shash_release(tcp_ses);
+
 out_err:
 	if (tcp_ses) {
 		if (!IS_ERR(tcp_ses->hostname))
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 42688ec..0ec3e13 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -407,7 +407,7 @@ static int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len,
 	/* In particular we can examine sign flags */
 	/* BB spec says that if AvId field of MsvAvTimestamp is populated then
 		we must set the MIC field of the AUTHENTICATE_MESSAGE */
-
+	ses->server->ntlmssp.server_flags = le32_to_cpu(pblob->NegotiateFlags);
 	tioffset = cpu_to_le16(pblob->TargetInfoArray.BufferOffset);
 	tilen = cpu_to_le16(pblob->TargetInfoArray.Length);
 	ses->tilen = tilen;
@@ -443,10 +443,12 @@ static void build_ntlmssp_negotiate_blob(unsigned char *pbuffer,
 		NTLMSSP_NEGOTIATE_128 | NTLMSSP_NEGOTIATE_UNICODE |
 		NTLMSSP_NEGOTIATE_NTLM;
 	if (ses->server->secMode &
-	   (SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED))
+			(SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED)) {
 		flags |= NTLMSSP_NEGOTIATE_SIGN;
-	if (ses->server->secMode & SECMODE_SIGN_REQUIRED)
-		flags |= NTLMSSP_NEGOTIATE_ALWAYS_SIGN;
+		if (!ses->server->cphready)
+			flags |= NTLMSSP_NEGOTIATE_KEY_XCH |
+				NTLMSSP_NEGOTIATE_EXTENDED_SEC;
+	}
 
 	sec_blob->NegotiateFlags |= cpu_to_le32(flags);
 
@@ -552,9 +554,19 @@ static int build_ntlmssp_auth_blob(unsigned char *pbuffer,
 	sec_blob->WorkstationName.MaximumLength = 0;
 	tmp += 2;
 
-	sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
-	sec_blob->SessionKey.Length = 0;
-	sec_blob->SessionKey.MaximumLength = 0;
+	if ((ses->server->ntlmssp.server_flags & NTLMSSP_NEGOTIATE_KEY_XCH) &&
+			!calc_seckey(ses->server)) {
+		memcpy(tmp, ses->server->ntlmssp.ciphertext, CIFS_CPHTXT_SIZE);
+		sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
+		sec_blob->SessionKey.Length = cpu_to_le16(CIFS_CPHTXT_SIZE);
+		sec_blob->SessionKey.MaximumLength =
+				cpu_to_le16(CIFS_CPHTXT_SIZE);
+		tmp += CIFS_CPHTXT_SIZE;
+	} else {
+		sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
+		sec_blob->SessionKey.Length = 0;
+		sec_blob->SessionKey.MaximumLength = 0;
+	}
 
 setup_ntlmv2_ret:
 	return tmp - pbuffer;
-- 
1.6.0.2